The invention relates to a bone shaping system made up of an instrument holder and a surgical instrument for attachment to the holder. The holder includes a shank equipped with a head designed to receive an instrument, and an annular locking component mounted so as to slide about the shank, under the head, equipped with locking means which cooperate with the head so as to lock the instrument on the head, and pushed against the head by a helical spring.
One such system is described in European Patent 0782840, the content of which is incorporated herein by reference thereto, and includes a shaft (10), equipped at one end with a cutting head holder (12) which has a bayonet joint and lock. A hemispherical or conical rotary cutting head (1) has inner radial rods (4) to engage with the bayonet joint. The cutting head contains an axial guide tube (5) between the inner ends of the radial rods and a central aperture (3) to receive a twist drill (9) which makes a hole in the middle of the recess formed by the cutting head. The lower end of the guide tube has one or more notches to receive corresponding studs on the twist drill so they rotate together. The holder (12) has a projection to block the drill in the guide tube. Additionally, the end of the guide tube, which adjoins the centre of the cutting head, has at least two projecting cutting teeth. Where a central hole in the recess is not required, a shorter twist drill is employed. However, while useful for controlling the cutting of the acetabulum, this system does not foresee a sliding fit between the reamer and the twist drill but rather one in which the two rotate together as a unit. Further, it is not contemplated that the drill be affixed to the bone and subsequently be used for guidance.
Other systems provide for reshaping of the bone, but the tool itself generally obstructs the view of the femoral lobe during cutting.
Therefore, there is a needed for cutters capable of cutting and shaping the femoral joint in preparation for the reception of a prosthetic cap. Such an application presents other challenges in guidance and control, particularly that of ensuring that the stem of the femoral joint is not damaged in the process.
What is needed therefore is a system which enables controlled cutting and reshaping of the femoral joint in preparation for the reception of a femoral cap prosthesis. What is needed is a system which does not completely obstruct the view of the femoral lobe when the reamer is placed over the lobe, ready for cutting or process thereof. Further, what is needed is a system that controls heat by moving any points of heat generation from the reamer to the holder, and thus away from the operative site.